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991.
C. Cativiela M. D. Diaz De Villegas E. Melndez 《Journal of heterocyclic chemistry》1985,22(6):1655-1657
Several Z-2-methyl(or phenyl)-4-[α-arylethylidene]-5(4H)-oxazolones 3Z, 4Z were prepared. The results obtained were compared by diazomethane insertion and condensation procedure. In order to synthesize E-2-phenyl-4-[α-arylethylidene]-5(4H)-oxazolones 4E hydrogen bromide isomerization in dry benzene was used. 相似文献
992.
W. Jeitschko D.J. Braun R.H. Ashcraft R. Marchand 《Journal of solid state chemistry》1978,25(4):309-313
Twenty-six ternary phosphides Ln2T12P7 (Ln = lanthanoid, T = Fe, Co, Ni) were prepared for the first time by reaction of the elemental components in liquid tin or by reaction of the components in evacuated silica tubes. The analysis of their powder patterns indicates their isotypism with Zr2Fe12P7. Their lattice constants are reported. Gd2Ni12As7 also crystallizes with that structure. 相似文献
993.
4-Isothiazolin-3-one 1-oxides and 1,1-dioxides react with a variety of cyclic and acyclic dienes to afford cycloaddition products. 相似文献
994.
C.N.R. Rao Om Parkash D. Bahadur P. Ganguly S. Nagabhushana 《Journal of solid state chemistry》1977,22(3):353-360
Electronic and magnetic properties of Ln1?xSrxCoO3 (Ln = Pr, Nd, Sm, Eu, and Gd) systems show that above a critical value of x, the d electrons become itinerant while the materials become ferromagnetic at low temperatures. The ferromagnetic component increases with increase in x and decrease in temperature. The Curie temperature increases with x and decreases with decrease in the size of the rare-earth ion. Incorporation of Ba2+ in LaCoO3 favors itinerant electron ferromagnetism relative to Sr2+ while Ca2+ is less favorable than Sr2+. 相似文献
995.
The GPC elution behaviour of a polymer was studied when a solution of another polymer in a liquid was used as an eluent. In ternary systems containing two polymers, GPC results are influenced by the thermodynamics of polymer incompatibility. The incompatibility manifests itself both in the slope of the dependence of elution volume upon the concentration of injected polymer and in the shift of elution volumes extrapolated to zero concentration. Experimental data for systems containing poly(styrene) and poly(methyl methacrylate) have been accounted for qualitatively by theoretical views on coil shrinkage resulting from polymer incompatibility. The concentration effects of the injected polymer and the polymer in the mobile phase on elution volume are compared; further parameters affecting the separation in the systems with polymer solution as eluent are discussed. 相似文献
996.
W E May S N Chesler S P Cram B H Gump H S Hertz D P Enagonio S M Dyszel 《Journal of chromatographic science》1975,13(11):535-540
The low concentration of hydrocarbons anticipated in pollution baseline studies necessitates the development of analytical techniques sensitive at the sub-microgram per kilogram concentration level. The method of analysis developed in this laboratory involves dynamic headspace sampling for volatile hydrocarbon components of the sample, followed by coupled-column liquid chromatography for the non-volatile components. These techniques require minimal sample handling, reducing the risk of sample component loss and/or sample contamination. Volatile sample components are separated from the matrix in a closed system and concentrated on a TENAX-GC packed pre-column, free from large amounts of solvent and ready for GC/GC-MS analysis. Non-volatile compounds, such as the benzpyrenes, may be extracted from large volumes of water and concentrated on a Bondapak C18 packed pre-column for coupled-column liquid chromatographic separation and analysis. Results of the application of these techniques to the analysis of samples from sites of known low level hydrocarbon contamination are presented and discussed. 相似文献
997.
The construction and properties of a new urea-sensing membrane electrode capable of making direct urea measurements in whole blood are described. The electrode has a layered structure in which a small quantity of EDTA-stabilized urease enzyme solution is held between an external dialysis membrane and the gas-permeable membrane of a conventional ammonia selective electrode. It is shown that the electrode functions reliably in whole blood samples, used with minimal pretreatment, as well as in serum or aqueous solutions. The range, dynamic response, lifetime, precision, and accuracy of the electrode system are appropriate for clinical measurements in whole blood or serum, and promise to simplify such analyses with an attendant reduction in costs. 相似文献
998.
Journal of Thermal Analysis and Calorimetry - Die Acetate Mg(OCOCH3)2 · 4H2O, Ca(OCOCH3)2 · H2O, Mn(OCOCH3)2 · 4H2O, Co(OCOCH3)2 · 4H2O, Ni(OCOCH3)2 · 4H2O,... 相似文献
999.
Summary Mutual diffusion coefficients of two gases A and B can be determined in an empty gas chromatographic column by letting component B enter at an intermediate position of the column and continuously flow through a part only of it, as a carrier gas. The other component A is injected in a small amount instantaneously at the closed end of the column with the detector placed at the other end. By repeatedly stopping and then restoring after a short time the flow of B, narrow extra peaks are produced on the chromatographic elution curve, owing to diffusion of A into B. An equation is derived giving the area under the curve of each stop-peak as a function of time of the corresponding stop. Plotting the experimental data according to this equation permits the determination of the diffusion coefficient of A into B. Some results obtained by this method show negligible variations with changes in the experimental parameters. 相似文献
1000.
H. D. Hollis Showalter John M. Domagala Joseph P. Sanchez 《Journal of heterocyclic chemistry》1981,18(8):1609-1612
Starting from readily available 1,2-dihydro-6-methyl-2-oxo-3-pyridinecarbonitrile, 1, viable synthetic pathways to a number of C-6 functionalized 1,2-dihydro-2-oxo-3-pyridinecarbonitriles and corresponding acids are presented. Through the utilization of dianion chemistry, the C-6 methyl substituent is selectively functionalized to three different oxidation levels. 相似文献